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Post by cravenscoot on Aug 25, 2013 15:56:03 GMT -5
 Hi all, I have a standard issue 139mb. I have been working on it for over a week. Guy I bought it from said the carb was bad. I cleaned the carb, over and over again, would start after that but no throttle controle at all and wouldn't idle. I broke down and got a new carb. I hooked it up and it fired right up and idled and ran fine. I turned it off to start again to make sure i was ready for a scoot and it started but had the same problem as before. Ive checked the spark as well as all the wireing, seems fine. is there something im missing. it seems like ive determined everthing mechanicly is working. electricly im not sure. is there something electricly that would cause it to not want to idle, and have no throttle control(when it does run it just chugs at a low rpm and will not throttle up) batt is new as well. uuuurrrgggghhhh! 
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Post by carasdad on Aug 25, 2013 16:12:40 GMT -5
How many miles on it?.. May be a valve adjustment problem.  |
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Post by cravenscoot on Aug 25, 2013 16:20:25 GMT -5
It says 1682 miles, but not sure if thats correct. the speedo doesnt work so prob. not. when I put the new carb on it, it started right up after getting the gas to the carb, and ran like a raped ape. It reved up fine and idled great, which it had not done before the new carb. I turned it off and cranked it again and it did what it did when I got it. which was starting only when holding throttle all the way down, even then it just chugged at low rpm's with no response in the throttle and had to keep throttle all the way down to keep it running, when let off it stals right out.
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Post by PCBGY6 on Aug 25, 2013 17:25:56 GMT -5
If it sat for a long time you may want to drain all the gas out of the tank and lines. If the fuel has trash it then that could explain why it's running bad with the new carb. It also could've taken a minute for the trash to get to the carb.
At this point I would pull the carb of and drain the fuel into something that I could view it in. Check the fuel filter also.
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Post by freefour1968 on Aug 25, 2013 23:28:35 GMT -5
Might want to change that fuel filter too, it maybe clogged up , new carb with filled bowl would run fine till the gas stopped coming in . DX
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Post by geh3333 on Aug 26, 2013 0:26:11 GMT -5
Like they said change the filter and clean out the gas tank. U may want to clean the new carb out also if the filter and gas was bad " dirty" .
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Post by rae4180 on Aug 26, 2013 6:44:57 GMT -5
sounds like whats going on with my scoot to. Im thinking the pedcock is stuck open and it lets to much gas in at one time so the scoot will bog down.
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Post by geh3333 on Aug 26, 2013 9:33:44 GMT -5
Even if its stuck open the float in the carb will not let to much gas flow in. Thatswhy many including myself remov the junk fuel valve and replace it with a manual shutoff valve.
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Post by cravenscoot on Aug 26, 2013 9:50:56 GMT -5
I did take off the Tank and drain it last night. Im not sure how old it was. smelled ok, but that doesnt mean anything I suppose. I cleaned the carb that came on it before I bought the new one and got the same action out of the new as the one that was "Dirty". However I pulled the diaphram cover while I had the old carb on and when I took the diaphram and pin out it ran wonderful once it got all that air straight to the carb. I did however realize that you cant drive it with it like that. Just an observation. I think the coil might not have the proper spark going to the plug. When I pull the plug and ground it out it just doesnt seem to have any emphhhh to it. Could that be a good thing to replace? Or am I way off?
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Post by oldchopperguy on Aug 26, 2013 13:40:38 GMT -5
Since it ran once like it should (sort of) but now won't accelerate and needs the throttle open to start... I'm thinking the electronic "choke" or richener may be stuck open. Then, when you start it with throttle open, it gets enough air to run, but that's all. Then the over-rich condition makes it choke on too much fuel.
Only a guess, but since it did the same thing even with the NEW carb, it's possible there's an electrical glitch keeping the choke on.
Something to check anyway...
Leo in Texas
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Post by geh3333 on Aug 26, 2013 20:24:44 GMT -5
DX check voltage to the choke. If thdre is none thats your prob
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Post by cravenscoot on Aug 27, 2013 7:56:20 GMT -5
OK guy's, here is my update. I replaced the ignition coil to the commonly found orange performance model, It started and ran great, and I drove it 12 miles yesterday.  However after I turn it off it wont start til after 20 or 30 min of cooling. I have replaced everthing electrical but the CDI so i'm getting pretty close. My buddy believes that the CDI is the last piece of the puzzle. He says that after it heats up it malfunction's when you try an start it again, and that once it cool's it function's properly. Make any sense? Anyone have knowledge? |
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Post by oldchopperguy on Aug 27, 2013 11:55:33 GMT -5
OK guy's, here is my update. I replaced the ignition coil to the commonly found orange performance model, It started and ran great, and I drove it 12 miles yesterday.  However after I turn it off it wont start til after 20 or 30 min of cooling. I have replaced everthing electrical but the CDI so i'm getting pretty close. My buddy believes that the CDI is the last piece of the puzzle. He says that after it heats up it malfunction's when you try an start it again, and that once it cool's it function's properly. Make any sense? Anyone have knowledge? My original factory CDI did all sorts of weird things within the first month. (back then, I knew little about these and was still learning... Old Harley guy, 6-volt, points & condenser, etc. ...)I had the no-hot-start problem. Poor idle, wouldn't rev beyond 6K... I simply replaced the CDI because it was the easiest and cheapest thing to try first... LOL! I used a "red" one. I immediately got fairly decent running. I still had a long way to go to get it all right though. After the CDI replacement, I did the orange Bando coil. Ran still better. Then the iridium plug, and a little better yet. Short story is that I still had to get rid of the factory air-filter system and run ONLY a UNI-sock filter, then carefully tweak the carb until it was as good as it could get. CDI's sometimes go bad all at once, and just "die". Sometimes the slowly go bad like my original, and give you fits wondering what's up. I'd replace it, AND I'd buy a second "back-up" CDI to keep on hand for the future. Test-run it though, since it is POSSIBLE to get a "dead" one brand-new. No guaranty that a CDI will fix your problem, but the chances are very good!Ride safe, Leo in Texas |
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Post by cravenscoot on Aug 27, 2013 12:03:06 GMT -5
Thanx everyone, your guys words of wisdom helped me narrow down and somewhat confirm my problems. I'll let you guys know how the CDI replacement pan out. |
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